It's a free online statistics textbook, also available in print. I haven't used it extensively, so I can't vouch for its quality -- actually, I complain about it a bit in Statistics Done Wrong. But I've never come across a very good conceptual introduction to statistics, so this is roughly the best I know.

There are also amusing variations, like the cartoon guide to statistics:

The test is running only for 12s. It should at least run for a couple of minutes and several times with a clear control of what is going on on the server at the same time.

You do not even know the memory load, what was running at the same time on the server, etc. It is like throwing one blue dice and one yellow. You get a six on the first and a three on the second and consider through your not terribly scientific benchmark that you get more with blue dices.